The Third Generation Partnership Project (3GPP) unites a number of telecommunications standard development organizations and provides their members with an environment in which to develop specifications for cellular telecommunications network technologies, including radio access, the core transport network, and service capabilities. 3GPP specifications also provide hooks for non-radio access to the core network, and for interworking with other networks.
More recently 3GPP introduced the Power Savings Mode (PSM) feature. PSM is a new user equipment (UE) state where the UE can stop listening for paging, stop performing idle mode procedures, etc. When the UE is in this state, it may not be reachable for mobile terminated (MT) communications. While the UE may certainly benefit from energy savings, other entities, such as for example, a Service Capability Server (SCS), lack control or awareness as to whether the UE is using the PSM feature. Likewise, the UE is unaware of when the SCS will need to reach the UE. Thus, the UE may not know the best time to invoke PSM.
The PSM feature presently allows the UE to ask the Mobile Management Entity (MME) to go into PSM mode for a predetermined amount of time. The MME has authority over whether the UE's request should be granted. Thus, a SCS cannot prevent a UE from entering a PSM state. The SCS also cannot control the instant the UE enters the PSM state, as well as the duration of the PSM state. Separately, the SCS is not apprised as to when the UE moves into and out of a PSM state. Without this information, the SCS cannot efficiently initiate and/or schedule its MT communication with the UE. Since many of the PSM capable devices are low power/low cost devices, it is important to avoid retransmission of data to these devices to avoid higher power consumption, wastage of network resources, and patchy communication with the device.
Further, the PSM feature requires that the UE request a value for ‘Periodic Tracking Area Update (TAU)’ and the ‘Active time’. The requested times depend upon when the UE anticipates that it will need to be available for MT data. While the MME decides the final value of these timers, the MME cannot initiate the request to provide an active timer for the UE.